Photochromoscopic and trichromatic apparatus.



Draftsman.

Patented July I, I902.

F. E. IVES. PHOTOCHROMDSCOPIC AND TRICHROMATIC APPARATUS.

(Application filed may 21, 1002.!

(No Model.)

ra a f I jnb'arcmrflecting and transmitting devices constructed UNITED STATES PATENT OFFICE.

PHOTOCHROMOSCOPIC AND TRICHROMATIC APPARATUS. I

SPECIFICATION forming part of Letters Patent N 0. 703,929, dated July 1, 1902.

Application filed May 21,1902. Serial No. 108,3 84:, No model.)

1'0 all whom, it nmy concern.-

Be it known that I, FREDERIL" E. IVES, a citizen of the United States, residing in Philadelphia, Pennsylvania, have invented certain Improvements in Photochromoscopic and Trichromatic Apparatus, of which the following is a specification.

The object of my invention is to provide an improved substitute for the transparent re flectors of clear or colored or thinly-silvered or platinized plates of glass which are employed in various forms of photochromoscopic or triohromatic apparatus for dividing the light into three or more portions in' order to form three or more images with light coming from one view-point or to optically superpose three or more images to the eye. This objectI attain in the manner hereinafter set forth,'reference being had to the accompanying drawings, in which Figures 1 and 2 are views showing lightrein accordance with my present invention. Figs. 3, 4, and 5 are perspective views of,an element of a compound prism constituting one of the features of my invention, and Fig. 6 is a diagrammatic view of a trichromatic camera in which one of said compound prisms is employed.

Clear or colored transparent-glass reflectors, although eflicient when properly used in photochromoscopic or trichromatic apparatus, have certain defects which it is advisable to eliminate. When clear glasses are used, it is necessary to provide combinations which will parallelize the rays of light which form the two reflections in order to avoid doubling of outlines, and colored-glass reflectors do not reflect as much light as is sometimes desirable to equalize the illumination of the difierent colors. Moreover, both clear and colored glasses have polarizing properties which may introduce errors in the performance of the apparatus, and the inclination of glass plates in a cone of rays introduces an image distortion which cannot be perfectly corrected without further elaboration of optical parts, involving some loss of light. Thinly-silvered mirrors are also very easily injured and rendered useless. In order to avoid these defects, I substitute. for a plate-glass reflector a compound prism, preferably two rectangular .nris m emented together, with one of the internal surfaces thinly silvered, or, if provided with an opaque metallic reflecting-film,havin g the latter broken by lines or equivalent openings in the film, which are suiflciently open to avoid the introduction of destructive diifraction effects. In the accompanying drawings such compound prisms are represented in Figs. 1 and 2, in each of which figures two rectangular prisms are represented, respectively at 1 and 2, these prisms having their diagonal faces cemented together, such face of either prism being provided with a thin coating or deposit of silver or other metal, as shown at 3 in Fig. 1, or, if provided with an opaque metallic coating or film 3, having the same broken by openings-such as lines, dashes, dots, or the like-distributed throughout the areaof the film, the prisms shown in Figs. 2,

3, 4, and 5 having the metallic film broken by parallel lines about equaling in width the intervening portions of the film. Such a reflecting and transmitting device, if employed in proper relation to alens of sufficient aperto re, will not interfere with the formation of a complete image by both the reflected and transmitted rays. Either of the devices shown in Figs. 1 and 2 overcomes the objections noted as attending the use of inclined plate-reflectors, the direction of the incident rays being represented at w, of the reflected rays at m, and of the transmitted rays at y.

Fig. 6 shows asimple form of trichromatic camera in which a light reflecting and transmitting device such as shown in Fig. 1 is utilized for dividing the rays of light which go to form the red and green images, a plateglass reflector serving to reflect the rays which form the blue image and transmit the rays which form the red and green images. In this case 5, 6, and 7 represent ordinary photographic cameras, 5, 6, and 7, respectively, the blue, green, and red color screens employedin connection therewith, 8 the compound prism, and 9 a yellow-glass reflector for separating the rays which are to form the blue image from those which are to form the red and green images. A compound prism can be substituted for the reflector 9, but the greater sensitiveness of a photographic plate to the blue rays makes the plate-glass reflector efficient, whereas a reflector of this character occupying the position of the reflectingsurface of the compoundprism 8 might not reflect sufiicient light to approximately equalize the working apertures of the lenses belonging to the cameras 6 and 7, as is desirable in order to give the greatest possible effective light-intensity for the whole combination.

The transparent-refiector system may be contained within a box-like inclosure 10, with aperture at the front for the passage of the incident rays.

When two of the compound prisms are used each having a lined opaque reflecting-surface, the lines of one prism should be at an angle, preferablya right angle, in respect to those of the other.

A compound prism such as I have shown and described might be substituted for one or more of the transparent glass mirrors in any of the various forms of photochromoscopic apparatus shown in my prior patents and in which plates of glass are employed as such transparent mirrors.

Having thus described my invention, I claim and desire to secure by Letters Patent 1. In apparatus of the character described, a compound prism with internal light reflecting and transmitting surface as a means of dividing the rays of light which form two colored images.

In apparatus of the character described, a compound prism with internal light reflecting and transmitting surface as a means of dividing the rays of light to form two images, in combination with appropriate color screens for said divided rays.

3. In apparatus of the character described, the combination of a compound prism with internal light reflecting and transmitting surface for dividing the rays which form two images, and a plate-reflector for separating from the incident rays those which form a third image.

4. A light reflecting and transmitting device consisting of a prism having its inclined face provided with an opaque film, having breaks or openings therein distributed throughout the area of the film.

5. A light reflecting and transmitting device consisting of a compound prism formed of two prisms with their diagonal faces secured together, one of such faces having an opaque film with breaks or openings therein distributed throughout the area of the film.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

FREDERIC E. IVES.

itnesses:

F. E. BECHTOLD, .Tos. H. KLEIN. 

